Thanks for your replies, everyone. It has given us a lot to think about. Personally, I think we would be happy on both lines and now it seems to be down to cost and itinerary. I can see that Oceania is more expensive, but when you look at it closely, there many things added in the price that we pay extra for on Celebrity.
On a completely different note - does anyone know where you would fly in to or out of if you go to Haifa. We are looking at a Holy Land Cruise if possible as they look amazing.